This supplemental research proposal mainly concerns the study of four metabolic errors of amino acids utilizing the fibroblast culture technique. The enzyme defects in hyperornithinemia, "new" variant types of argininosuccinic aciduria and maple syrup urine disease, and non- ketotic hyperglycinemia will be investigated in depth. In hyperornithinemia with hyperammonemia and homocitrullinuria, ornithine decarboxylase will be studied with particular attention to enzyme kinetics and cofactor requirements. Variant types of argininosuccinic aciduria and maple syrup urine disease will also be investigated in terms of enzyme kinetics. The electrophoretic mobility of argininosuccinase will be studied in fibroblasts from normal individuals and those with variants of argininosuccinic aciduria. Glycine and valine metabolism and their possible interrelationships will be studied in fibroblasts of infants and children with non-ketotic hyperglycinemia.